EP1197731B1 - Sensor system with adjustable sensor signal processing - Google Patents

Description

The invention relates to a sensor system with variable sensor signal processing according to the preamble of claim 1, and to a method for changing the signal processing in a sensor system according to the preamble of claim 10.

The known systems and methods, from which the invention proceeds, are known from the prior art in a variety of modifications. Typical sensor systems are for example in " Hütte - The Foundations of Engineering, Publisher: Akademischer Verein Hütte ev, Berlin, edited by Horst Czichos, 30th revised and expanded edition, Berlin: Springer Verlag 1996, page H 18 ff The sensor unit is based essentially on at least one sensor element for detecting a measured variable and for generating a sensor signal representing the measured variable, and a sensor signal processing unit for processing a measured variable representing the process variable Sensor signal according to predetermined parameters.

The evaluation unit is provided for an evaluation of sensor signals processed by the sensor signal processing unit.

• Sensoren, bei denen die Sensorsignalverarbeitung in der Sensorsignalverarbeitungseinheit nach festen Algorithmen erfolgt (Typ 1),
• Sensoren, bei denen die Sensorsignalverarbeitung in der Sensorsignalverarbeitungseinheit frei programmierbar ist (Typ P),
• Sensoren, bei der die Sensorsignalverarbeitung geregelt erfolgt (Typ R) und
• Sensoren bei denen die Sensorsignalverarbeitung in der Sensorsignalverarbeitungseinheit sowohl programmierbar als auch regelbar ist.

In the prior art, a variety of sensor types are distinguishable. By way of example, four main types are presented below. In detail these are:

• Sensors in which the sensor signal processing in the sensor signal processing unit takes place according to fixed algorithms (type 1),
• Sensors in which the sensor signal processing in the sensor signal processing unit is freely programmable (type P),
• Sensors in which the sensor signal processing is controlled (type R) and
• Sensors in which the sensor signal processing in the sensor signal processing unit is both programmable and controllable.

1.) Type 1 sensors:

Sensor systems with fixed signal processing algorithms

The most widespread are sensor systems which, according to fixed algorithms, convert a generally analogous physical or chemical measured variable (M) into an output signal. As a physical measured variable, pressure, temperature and magnetic field are examples. As a chemical parameter, for example, the reaction rate in the chemical reaction and the reaction enthalpy or the like. into consideration.

The sensor element itself first converts the physical (or chemical) measured quantity (M) into an internal voltage signal U (M). However, it is also possible for a current signal dependent on the measured variable M or an optical signal dependent on the measured variable M to be generated.

The following statements relate to sensor elements in which a physical measured variable M is converted into an internal voltage signal U (M), wherein the amplitude of the internal voltage signal U (M) represents the physical measured variable M. However, this assumption applies without restriction to the general public.

The output signal (Out) of most sensor units is the measured variable M proportional. However, there are types, in particular in the case of magnetic field sensors, which transform an analog measured variable M into an output signal (Out) which has only two states. As a rule, one speaks of switching sensors.

Such sensor units (switching sensors) have two predefined threshold values G ₁ and G ₂ . In the following let abd G ₁ > G ₂ . These produce on the output side a signal Out = "1" if the internal voltage signal U (M)> G ₁ , and an output signal Out = "0", if U (M) <G ₂ : $${\mathrm{Out}}_{\mathrm{New}}=\{\begin{array}{cc}\mathrm{1}.& \mathrm{if}\left(\mathrm{U}\left(\mathrm{M}\right)>{\mathrm{<figure-callout\; id="1"\; label="G"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">G</figure-callout>}}_{\mathrm{1}}\mathrm{\Lambda }{\mathrm{Out}}_{\mathrm{old}}=\mathrm{0}\right)\\ \mathrm{0}.& \mathrm{if}\left(\mathrm{U}\left(\mathrm{M}\right)<{\mathrm{G}}_{\mathrm{2}}\mathrm{\Lambda }{\mathrm{Out}}_{\mathrm{old}}=\mathrm{1}\right)\end{array}$$

2.) Type P sensors: sensor systems with freely programmable algorithms

in den Parametern c₁ und c₂ programmiert werden. Der Vorteil gegenüber den Sensoren vom Typ 1 besteht darin, daß durch die Programmierung fertigungsbedingte Streuungen und Einflußeffekte durch Wechselwirkungen des Sensorsystems mit seiner Wirkung reduziert werden können.In addition to sensor units, where the Sensorignalverarbeittung run according to fixed algorithms, there are types in which This algorithm, according to which the measured variable M is converted into an output signal Out, can be freely programmed with the aid of predefined parameters. These fixed parameters are stored for example in EEPROM cells which are located on the same chip as the other components - the sensor element and the sensor signal processing unit - the sensor unit. An example of this is the analog sensor of the HAL800 series from the manufacturer MICRONAS. Its analog output signal can be used as $$\mathrm{Out}={\mathrm{<figure-callout\; id="1"\; label="c"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">c</figure-callout>}}_{\mathrm{1}}*\mathrm{U}\left(\mathrm{M}\right)+{\mathrm{c}}_{\mathrm{2}}$$

programmed in the parameters c ₁ and c ₂ . The advantage over the sensors of type 1 is that through the programming production-related scattering and influence effects can be reduced by interactions of the sensor system with its effect.

If the programming operation is completed, the sensor unit behaves like a type 1 sensor unit. The sensor unit therefore has fixed settings with which the measured variable M is converted into an output signal Out. The programming settings are no longer changeable. In technical terms, this condition is referred to as "locked".

3.) Type R sensors: sensor units with control algorithms

In a third class of sensor units, the sensor signal processing unit operates with internal control algorithms. Such control algorithms convert a time-varying analog internal voltage signal U (M, t) into an output signal Out. (The time dependence of the internal voltage signal U (M) is indicated by the reference symbol t.)

$${\mathrm{Out}}_{\mathrm{neu}}=\{\begin{array}{cc}\mathrm{1},& \mathrm{wenn}\left(\mathrm{U}\left({\mathrm{M}}_{\mathrm{AC}}\right)>{\mathrm{G}}_{\mathrm{1}}\mathrm{\Lambda }{\mathrm{Out}}_{\mathrm{alt}}=\mathrm{0}\right)\\ \mathrm{0},& \mathrm{wenn}\left(\mathrm{U}\left({\mathrm{M}}_{\mathrm{AC}}\right)<{\mathrm{G}}_{\mathrm{2}}\mathrm{\Lambda }{\mathrm{Out}}_{\mathrm{alt}}=\mathrm{1}\right)\end{array}$$

For example, there are adaptive magnetic field sensors in which a high-pass filtering of the internal voltage signal U (M) is performed. In concrete terms, this means that a DC component of the internal voltage signal U (M) is subtracted and, ideally, only a sinusoidal alternating signal U (M _AC ) remains. If this remaining sinusoidal alternating signal exceeds a predetermined threshold value G ₁ , as in the example described above, an output state Out = "1" is generated, if the alternating component is less than a second threshold value G ₂ , the output signal Out = "0". The mathematical representation of such an output signal formation is shown in equation (3): $$\mathrm{U}\left({\mathrm{M}}_{\mathrm{AC}}\right)\Rightarrow \mathrm{U}\left(\mathrm{M}\right)-\underset{{\mathrm{t}}_{\mathrm{1}}}{\overset{{\mathrm{t}}_{\mathrm{2}}}{\int }}\mathrm{U}\left(\mathrm{M}\right)\mathrm{dt}$$

$${\mathrm{Out}}_{\mathrm{New}}=\{\begin{array}{cc}\mathrm{1}.& \mathrm{if}\left(\mathrm{U}\left({\mathrm{M}}_{\mathrm{AC}}\right)>{\mathrm{<figure-callout\; id="1"\; label="G"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">G</figure-callout>}}_{\mathrm{1}}\mathrm{\Lambda }{\mathrm{Out}}_{\mathrm{old}}=\mathrm{0}\right)\\ \mathrm{0}.& \mathrm{if}\left(\mathrm{U}\left({\mathrm{M}}_{\mathrm{AC}}\right)<{\mathrm{G}}_{\mathrm{2}}\mathrm{\Lambda }{\mathrm{Out}}_{\mathrm{old}}=\mathrm{1}\right)\end{array}$$

Type R - sensors thus take into account, in contrast to the previously described types and the time course of the measured variable M.

4.) RP type sensors: programmable sensors Control algorithms

This fourth class of sensor units represents a combination of the types described under 2.) and 3.). Sensors of type RP thus combine the advantages of a sensor unit of type P and a sensor unit of type R. The free programmability of the signal processing guarantees on the one hand Adjustment of the tolerances of an overall system consisting of mechanical components and the actual sensor system, on the other hand it is ensured that a reaction of the output signal Out as a result of a control to the current time course of the measured variable M (t).

An essential problem of conventional sensor systems, which preferably operate according to the last-mentioned method, is that changes in the sensor system, in particular of the sensor element, can no longer be compensated within the life of the sensor unit.

From the DE 36 36,111 A1 For example, a remote calendering instrument system is known in which a transmitter, a receiver and a calibration device are connected by a two-wire transmission line. In the calibration mode of operation, the calibration device transmits calibration enable signals that cause the transmitter to raise a reference admittance for comparison with a detected admittance corresponding to a known physical state and monitor the bistable output signals transmitted by the transmitter that change state when the raised reference admittance shows a certain relation to the detected admittance.

From the DE 197 19 633 A1 is a measurement processing system for conditioning the measurement signal of at least one sensor, which has an internal interface and a consistent division of the functionality into a purely sensor-related sensor adaptation module a purely conditional matching module. The adjustment module comprises at least one operator adjustable voltage divider for setting a continuously or discretely variable parameter, which outputs a tuning voltage U_OUT via the interface to the sensor adapter module, which can be used there for purposes of zeroing or adjusting the trigger level, etc. In this case, the reference voltage on the input side of the reference divider voltage is set via the interface of the sensor adapter module. The range of values for the adjustment voltage adjustable by the operator by the sensor adjustment module can be specified such that the entire adjustment range of the operator-settable voltage divider can be used for a sensor-specific value range, regardless of the absolute level of the adjustment voltage, which results in a consistently high accuracy of the same for all sensor types Adjustability allows.

From the EP 0 048 851 a correction method in digital electrical length or angle measuring devices is known in which intermediate values are formed from unchanged, supplied by the measuring device periodic scanning signals in an interpolator. Correction values are stored in a memory with which interpolation values can be corrected by mathematically allocating the correction values in the correct order in the respectively correct position to the aforementioned interpolation values in a correction device which contains a computer. The thus corrected interpolation values are displayed as exact measured values.

A disadvantage of these known sensor systems or methods for operating sensor systems is that when updating the sensor system is not guaranteed at the same time that a constant update of the parameter set in the evaluation can take place.

The invention has for its object to design the known methods such and further, that the problems described no longer appears. In particular, it should be ensured that optimum signal processing always takes place.

This object is achieved by a method having the features of the characterizing part of claim 1 according to the invention.

Advantageous embodiments of the developments of the invention are specified in the subclaims.

The essential idea of the invention is that the evaluation unit is designed in such a way that at least one parameter for signal processing can be newly determined on the basis of the output signals supplied by the sensor signal processing unit. Furthermore, the invention provides that at least one connecting line between the sensor signal processing unit and the evaluation unit represents a connection to a transmission of at least one of the newly determined parameters for sensor signal processing to the sensor signal processing unit. The sensor signal processing unit according to the invention is designed such that the newly transmitted

Sensor signal processing parameters replace the originally specified parameters.

Thus, according to the invention, the evaluation unit recalculates at least one of the parameters for signal processing and transmits at least one of these newly determined parameters via an existing connection line or a possibly already existing wireless (non-line-connected) connection path between the sensor unit and the evaluation unit to the signal processing unit. The sensor signal processing unit now sets the newly transmitted parameter instead of the corresponding old parameter. If the evaluation unit now determines by analysis of the sensor data and any other data that the sensor unit would have a better measured value acquisition with a changed parameter set, then the method according to the invention ensures that the sensor signal processing is carried out further with this new parameter set.

Furthermore, the invention provides that a necessary change of a parameter for signal processing in the current (sensor) operation can be determined. It is further provided that at least one of the newly determined parameters during operation to the signal processing unit is transferable, so that a constant update of the parameter set is ensured in the sensor signal processing unit. This embodiment of the invention is particularly imperative when the sensor system is working or should work in continuous operation.

In such a sensor system, it is necessary that the transmission process of a new parameter set the ongoing operation of the signal transmission from the sensor unit to the evaluation unit does not bother. This is especially important if an exact time allocation is to take place or if changes or disturbances are to be recognized immediately. For this reason, the invention provides a filter device, which only allows a transmission of determined parameters, if a signal transmission from the sensor unit is not disturbed thereby.

As a first variant of the invention it is provided that a connection line is used for transmitting the newly determined parameters, which is already required for data transmission from the sensor unit to the evaluation unit anyway. In this case, the connection line which is connected to the output provided for outputting the processed sensor signal is preferably used.

This variant has the advantage that no further connection line between the sensor unit, which is generally present in integrated form on a chip, with sensor element and signal processing unit and the externally arranged evaluation unit is required. This ensures in particular that this novel type of sensor system according to the invention is similar in terms of its mechanical and geometric structure to the old sensor system generation. An adaptation is therefore not required.

In a second variant, the invention provides that a common energy supply line of the sensor unit and the evaluation unit is used as a transmission line of the determined parameters. Also in this case, as in the previous example, it is ensured that an old system can be easily replaced by a sensor system according to the invention can be. In particular, for incorporation into a mass product, such compatibility is a mandatory requirement.

A third variant of the invention provides that at least one parameter can be transmitted by a change in an output load between the sensor signal processing unit and the evaluation unit. Such a load change can be caused in a conventional manner by the evaluation unit and thus generated outside the sensor unit.

A fourth variant of the invention provides that this output load is continuously variable, or that the output load is gradually changed.

Alternatively or additionally, the invention provides that at least one parameter can be transmitted by changing a supply voltage of the sensor unit. Such a modulation of the supply voltage of the sensor unit does not necessarily require that the sensor unit and evaluation unit are supplied by one and the same voltage source, but it is also possible that with the aid of a corresponding control line, the power supply of the sensor unit or in particular the sensor signal processing unit is modulated.

Such a sensor system or such a method is generally used in programmable sensor systems in which an evaluation unit (evaluation electronics) evaluates a sensor signal and any further signals present. The sensor is programmable in one or more parameters. During operation, the evaluation electronics determine that a parameter needs to be changed. On a channel that does not interfere with the transmission of the actual sensor signals for evaluation to the electronics, the sensor is informed of this change request. An example is a detection of magnetic field changes called a method that is used in particular for measuring the angular position of the crankshaft, camshaft and ABS in the motor vehicle.

Figur 1

eine Struktur einer ersten Ausführungsform eines erfindungsgemäßen Sensorsystems

Figur 2

eine Struktur einer zweiten Ausführungsform eines erfindungsgemäßen Sensorsystems.

Two embodiments of the invention are illustrated in the drawings and will be described in more detail below. Show it:

FIG. 1

a structure of a first embodiment of a sensor system according to the invention

FIG. 2

a structure of a second embodiment of a sensor system according to the invention.

The FIG. 1 shows a block diagram of a sensor system according to the invention, whose basic components can in principle also be part of a conventional sensor system. According to the invention, however, individual components of the sensor system receive additional functions, which are described below to be discribed. For the sake of clarity, separate block symbols relating to these additional functions of the circuit components are omitted below.

From the FIG. 1 are the basic components of a sensor system 1 refer to their standard functions, for example, from the cited reference "hut" can be removed. In the example, the sensor system 1 is based on a sensor unit 10 and an evaluation unit 40, which are supplied in the example with the aid of the power supply unit 50 with electrical energy.

The sensor unit 10 is usually accommodated on a silicon chip. The evaluation unit 40 is connected to the sensor unit 10 via a larger number of connecting lines. This is usually spatially separated from the sensor unit 10. The evaluation unit 40 may possibly be a small microcomputer or part of a larger automation system. Depending on the application, the connection between the sensor unit 10 and the evaluation unit 40 via a single line, via multiple lines or even a data bus. In the example, the sensor unit 10 consists of a sensor element 12 and an output signal generating unit 20 adjoining the sensor element 12. The output signal generating unit 20 consists in the example of a measured quantity processing unit 22, an adjoining amplifier unit 24 and the actual sensor signal processing unit 25.

The circuit blocks Meßgrößenaufbereitungseinheit 22 and amplifier unit 24 shown in the example are optional units, ie these circuit elements need not necessarily be part of the sensor unit 10. in the For example, these are given only for this purpose to show that the output signal generating unit 20 has circuit elements whose operation is not changeable from the outside and circuit elements - in the example the sensor processing unit 25 - in which the functions can be changed by external means.

The sensor signal processing unit 25 consists of an analog signal processing unit 27, an adjoining analog / digital converter and a digital signal processing unit 28 adjoining thereto. The analog signal processing unit 27 and the digital signal processing unit 28 are connected to a parameter memory 26 in the example.

The analog signal processing unit 27 is connected in the example with a larger number of signal outputs A ₁ , A ₂ ... A _k , A _{k + 1} ... A _K to the evaluation unit 40. In an analogous manner, there are a larger number of signal outputs D ₁ , D ₂ ... D _n , D _{n + 1} ... D _{N of} the digital processing unit 28, which are connected to the evaluation unit 40. Furthermore, the evaluation unit 40 has a larger number of control signal inputs S ₁ ... S _i , S _{i + 1} , ... S _I.

• Dem Eingang E₁ des Sensorelementes 12 wird eine chemische oder physikalische Meßgröße M zugeführt. Das Sensorelement 12 wandelt diese physikalische oder chemische Meßgröße M vorzugsweise in ein elektrisches Signal um. Das elektrische Signal wird in der Regel ein von der Meßgröße M abhängiges Spannungs- oder Stromsignal sein, dessen Amplitude sich mit der Meßgröße M ändert. Dieses elektrische Signal liegt nun ausgangsseitig am Ausgang E₂ des Sensorelementes 12 an. Der Ausgang E₂ des Sensorelementes 12 bildet gleichzeitig den Eingang einer Meßgrößenaufbereitungseinheit 22. Diese Meßgrößenaufbereitungseinheit 22 kann beispielsweise ein Stromspannungswandler sein. Es ist jedoch auch denkbar, daß dieser die vorzugsweise elektrische Eingangsgröße in ein optisches Signal wandelt. Im Beispiel ist angenommen, daß ein internes Spannungssignal U(M) erzeugt wird, dessen Amplitude im wesentlichen proportional zur Messgröße M ist.

The operation of such a sensor system 1 is as follows:

• The input E _{1 of} the sensor element 12 is a chemical or physical measured variable M is supplied. The sensor element 12 preferably converts this physical or chemical measured variable M into an electrical signal. The electrical signal will usually be dependent on the measured variable M voltage or current signal whose amplitude coincides with the measured variable M changes. This electrical signal now lies on the output side at the output E _{2 of} the sensor element 12. The output E _{2 of} the sensor element 12 simultaneously forms the input of a Meßgrößenaufbereitungseinheit 22. This Meßgrößenaufbereitungseinheit 22 may be, for example, a current-voltage converter. However, it is also conceivable that this converts the preferably electrical input into an optical signal. In the example, it is assumed that an internal voltage signal U (M) is generated whose amplitude is substantially proportional to the measured variable M.

Often it is necessary that this internal voltage signal U (M) is first amplified in an amplifier unit 24 in order to eliminate interference and to ensure proper signal processing. Such a processed internal voltage signal U (M) is now available at the output of the amplifier unit 24 for sensor signal processing. The output of the amplifier unit 24 simultaneously forms the input E _{3 of} the sensor signal processing unit 25.

In the sensor signal processing unit 25, this internal voltage signal U (M) is processed in its form in the form of an analog signal with the aid of the analog signal processing unit 27. For example, 27 integrations or differentiations can be performed in the analog signal processing unit. In the example it is indicated that each individual processing step may directly generate an output signal which can be tapped at the marked signal outputs A _1, A ₂ ... A _k, A _{k + 1} ..A _K.

In the example, this analog signal processing in the analog signal processing unit 27 is variable from the outside with the aid of a parameter set. This parameter set is stored for example in the parameter memory 26.

New generation sensor systems generally do without costly analog signal processing. Therefore, the circuit component analog signal processing unit 27 will generally not be part of the sensor signal processing unit 25. However, the exemplary implementation of such an analog signal processing unit 27 is intended to demonstrate that the present inventive concept is not limited solely to sensor systems with predominantly digital signal processing.

In the example, such an analog-processed signal is now supplied to an analog-to-digital converter 29, where it is generally supplied as an internal output signal to a digital signal processing unit 28. In this digital signal processing unit 28, the sensor signal is now processed in a manner known per se and then discharged on the output side directly as a parallel or serial signal, or possibly several parallel or serial signals are removed after different processing steps. Such an interface in the example with the aid of the signal outputs D _1, D ₂ ... D _n ..D _{n + 1,} ... D _N labeled.

According to the prior art, this digital signal processing in the digital signal processing unit 28 can be parameterized with the aid of a parameter set stored in the parameter memory 26. According to the prior art, EEPROM cells which are arranged on the same chip as the other components of the sensor unit 10 are preferably used as parameter memory 26.

• Unter der Annahme, daß die Analysemöglichkeiten der von der Sensoreinheit, insbesondere der Sensorsignalverarbeitungseinheit 25, gelieferten Sensordaten (wie die Signalausgänge D₁,D₂,...D_n,D_n+1..D_N;A₁,A₂..A_k..A_k+1, ...A_k) und eventuell vorhandener sonstiger Daten (gegebenenfalls übermittelt über die Steuersignalleitungen S₁...S_i,S_i+1...S_I) in der Auswertungseinheit 40 dazu führen, daß es günstig wäre, einen Parameter innerhalb der Sensoreinheit 10 (Parameterspeicher 26) zu ändern, ergibt sich folgender Datenverkehr:
• Beispielsweise könnte die Auswertungseinheit 40 berechnen, daß die Subtraktion des Wechselanteiles U(M_AC) im laufenden Betrieb noch einmal um einen Korrekturwert U korrigiert werden muss, um eine bessere Performance des Gesamtsystems zu erreichen. Die Berechnung der Korrekturgröße U erfolgt also außerhalb der Sensoreinheit 10 in der Auswertungseinheit 40. Die Korrekturgröße Δ U wird nun beispielsweise in der Digitalsignalverarbeitungseinheit 28, d. h. innerhalb der Sensoreinheit 10, eingestellt, so dass folgende Signalverarbeitung durchgeführt werden kann: $$U\left({\mathit{M}}_{\mathit{AC}}\right)\Rightarrow U\left(M\right)-\underset{{\mathrm{t}}_2}{\overset{{\mathrm{t}}_1}{\int }}U\left(M\right)\mathit{dt}+\mathrm{\Delta U}$$
  
  $${\mathrm{Out}}_{\mathrm{neu}}=\{\begin{array}{cc}\mathrm{1},& \mathrm{wenn}\left(\mathrm{U}\left({\mathrm{M}}_{\mathrm{AC}}\right)>{\mathrm{<figure-callout\; id="1"\; label="G"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">G</figure-callout>}}_{\mathrm{1}}\mathrm{\Lambda }{\mathrm{Out}}_{\mathrm{alt}}=\mathrm{0}\right)\\ \mathrm{0},& \mathrm{wenn}\left(\mathrm{U}\left({\mathrm{M}}_{\mathrm{AC}}\right)<{\mathrm{G}}_{\mathrm{2}}\mathrm{\Lambda }{\mathrm{Out}}_{\mathrm{alt}}=\mathrm{1}\right)\end{array}$$
  
  U(M_AC) stellt wiederum den Wechselanteil des internen Spannungssignals U(M) und Δ U die oben erwähnte Korrekturgröße dar. Das neue Ausgangssignal Out_neu unter scheidet sich wie im voran beschriebenen Beispiel vom ursprünglichen alten Ausgangssignal Out_alt, wenn der Wechselanteil U(M_AC), - welcher durch die Korrekturgröße Δ U eine Veränderung erfahren hat -, nun auf Grund dieser Änderung entsprechenden Schwellenwert G₁ über bzw. den Schwellenwert G₂ unterschritten hat.

Based on the description of how a Sensor system of type R should be explained in the example, the operation of a sensor system 1 according to the invention:

• Assuming that the analysis capabilities of the sensor data supplied by the sensor unit, in particular the sensor signal processing unit 25 (such as the signal outputs D ₁ , D ₂ , ... D _n , D _{n + 1} .. _{D N} ; A ₁ , A ₂ . .A _k ..A _{k + 1} , ... A _k ) and possibly existing other data (possibly transmitted via the control signal lines S ₁ ... S _i , S _{i + 1} ... S _I ) in the evaluation unit 40 thereto lead that it would be convenient to change a parameter within the sensor unit 10 (parameter memory 26), the following data traffic results:
• For example, the evaluation unit 40 could calculate that the subtraction of the alternating component U (M _AC ) during operation has to be corrected once again by a correction value U in order to achieve a better performance of the overall system. The correction quantity U is therefore calculated outside the sensor unit 10 in the evaluation unit 40. The correction quantity ΔU is now set, for example, in the digital signal processing unit 28, ie within the sensor unit 10, so that the following signal processing can be carried out: $$U\left({\mathit{M}}_{\mathit{AC}}\right)\Rightarrow U\left(M\right)-\underset{{\mathrm{t}}_2}{\overset{{\mathrm{t}}_1}{\int }}U\left(M\right)\mathit{dt}+\mathrm{.DELTA.U}$$
  
  $${\mathrm{Out}}_{\mathrm{New}}=\{\begin{array}{cc}\mathrm{1}.& \mathrm{if}\left(\mathrm{U}\left({\mathrm{M}}_{\mathrm{AC}}\right)>{\mathrm{<figure-callout\; id="1"\; label="G"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">G</figure-callout>}}_{\mathrm{1}}\mathrm{\Lambda }{\mathrm{Out}}_{\mathrm{old}}=\mathrm{0}\right)\\ \mathrm{0}.& \mathrm{if}\left(\mathrm{U}\left({\mathrm{M}}_{\mathrm{AC}}\right)<{\mathrm{G}}_{\mathrm{2}}\mathrm{\Lambda }{\mathrm{Out}}_{\mathrm{old}}=\mathrm{1}\right)\end{array}$$
  
  U (M _AC ) again sets the alternating component of the internal voltage signal U (M) and Δ U the above-mentioned correction quantity The new output signal Out _new differs, as in the example described above, from the original old output signal Out _alt when the alternating component U (M _AC ), which has undergone a change by the correction variable ΔU, now corresponding to this change Threshold G ₁ above or has fallen below the threshold G ₂ .

According to the invention a correction of the parameter set in the parameter memory 26 is possible in that the evaluation unit 40 during operation of the sensor unit 10 via one or more of the existing connection lines, which in the example with the reference numbers A ₁ , A ₂ ... A _k , A _{k + 1} , ... A _K , the value of the correction value Δ U transmits as a parameter.

This means, in particular, that the ongoing operation of the signal transmission from the sensor unit 10 to the evaluation unit 40 may not be disturbed by the transmission or transmission process. For example, in time-critical systems in motor vehicles, such as the rotation angle measurement on a gear (camshaft, crankshaft or ABS), the timing of the angle (Out _alt = "1" to Out _new = "0" or vice versa) must not be disturbed by the correction process ,

To further illustrate the invention, the FIG. 2 another sensor system 1 according to the invention, consisting of a sensor unit 10 and an evaluation unit 40 connected thereto via a connecting line A. Both components, the sensor unit 10 and the evaluation unit 40, are connected to the supply voltage U by an electrical power supply unit 50 via the supply line V. _B supplied with electrical energy. The sensor system 1, a physical or chemical quantity M can be fed, which in the sensor unit 10 is converted and processed in the manner described and can be transmitted as output signal Out via the connecting line A to the evaluation unit 40.

This signal processing in the sensor unit 10 is characterized in the example by the programmable parameters (c ₁ , c ₂ , c ₃ , ... c _m , c _{m + 1} , .. c _M ). Further, by way of example, two control signal lines assigned to the evaluation unit 40 are shown, via which the control signals s _i or s _{i + 1 can be} fed to the evaluation unit 40.

The FIG. 2 shows the interaction between analog measured variable M of the sensor unit 10 and the evaluation unit 40. The indicated by the reference numerals 14 and 15 arrows indicate the information or data flow direction of the determination of a measuring effect during operation of the sensor system 1. In particular, the arrow with the reference numeral "15" between the sensor unit 10 and the evaluation unit 40 indicates the data flow, as - in a programmed sensor unit 10 in the "Locked" state, data from the sensor unit (10) to the evaluation unit (40) are transmitted ,

In previously known sensors, there is only one possibility to influence the parameters c ₁ , c ₂ , c ₃ ... C _n .. C _M stored in the sensor unit (10) during operation. According to the invention, it is now provided that the evaluation unit (40) analyzes the signal Out (and optionally further operating parameters of the sensor unit 10). Advantageously, it is also possible to consult further, independent of the sensor unit, control signals s _i or s _{i + 1} to this analysis. The evaluation unit (40) now checks the validity of the parameter set c ₁ , c ₂ , c ₃ ... c _m ... c _M with the aid of the data available to it.

By way of example, a sensor system 1 will be considered in the following, in which the sensor unit (10), a system consisting of a permanent magnet and a toothed wheel, maps the rotation of the toothed wheel into a chronological pulse sequence by measuring its magnetic field. The output signal Out conveyed to the evaluation unit (10) consists of a sequence of "0" and "1" which can be transmitted, for example, via an open-collector output.

For the sake of simplicity, it is assumed that the possibilities of intervention of the evaluation unit (40) in the sensor signal processing (which is usually referred to as a sensor algorithm) are limited to a single parameter, the correction value Δ U. If it is determined by the evaluation unit (40) that this parameter, the correction quantity .DELTA.U is to be changed, it is provided according to the invention that this change requirement of the sensor unit (10) is transmitted by the load between the sensor unit (10) and the evaluation unit (40) is changed. This load change is caused in the evaluation unit (40) and thus generated outside the sensor unit (10). An example is the load, which results in a substantially constant voltage as a variable load current and is denoted by the reference symbol I _load .

Flows, for example, in normal operation average load current I ₀ in the signal load path, the sensor unit (10) by changing the output load with the load current I ₁ , which is greater than the average load current I ₀ in normal operation, be communicated, the correction quantity .DELTA.U should be increased. By changing the load current, for example, to a value I ₂ > I ₁ > I ₀ , a reduction in the correction quantity Δ U can also be transmitted. The change of the load current from I ₀ to I ₁ or I ₂ can be continuous or at a certain frequency.

The sensor unit has a circuit arrangement which can detect the change in the load current I _load from I ₀ to I ₁ or I ₂ and then varies the parameter corresponding to the correction quantity Δ U.

It should be noted that the time required for the sensor unit 10 to reliably recognize the change request of the evaluation unit 40 is known, so that the changed load I _{load is} maintained for a sufficiently long time. The signal processing unit or the sensor unit 10 then changes the value of the correction variable Δ U in a corresponding manner. A feedback to the evaluation unit 40 is not required. In this way, it is possible that the evaluation unit 40 initially continues to work with the changed load current I ₂ or I ₁ or, which is usually more useful, with the lowest load current I ₀ . The evaluation unit 40 will now further analyze whether the change was sufficient. If a further change is required, the evaluation unit 40 again requests this change. Preferably, a change is made with the smallest possible incremental.

According to the invention, further possibilities for the transmission of a modified parameter set c ₁ , c ₂ ... are conceivable. The prerequisite is, however, that the ongoing operation is not disturbed.

According to the invention, it is provided that this supply voltage U _{B of} the sensor unit 10 and / or the sensor signal processing unit (25) can be modulated. The sensor unit (10) recognizes on the basis of the modulation, which parameter c _i must be on the way in which and the amount by which modified. In the simplest case, it is always the same parameter, which is preferably increased or decreased in the smallest possible steps.

This results in a large number of possible fields of application. In general, programmable systems are suitable for this, in which an evaluation unit 40 evaluates a sensor signal and any further signals present. The sensor unit 10 must be freely programmable in one or more parameters c _i . An example of such systems is the sensing of magnetic field signals, for example for detecting and regulating the angular position of the crankshaft, the camshaft or the antilock brake system in a motor vehicle.

LIST OF REFERENCE NUMBERS

1

sensor system

10

sensor unit

12

sensor element

14

data flow

15

data flow

20

Output signal generation unit

22

Meßgrößenaufbereitungseinheit

24

amplifier unit

25

Sensor signal processing unit

26

parameter memory

27

Analog signal processing unit

28

Digital signal processing unit

29

Analog / digital converter

40

evaluation unit

50

Power supply unit

A

lead

AC

AC signal component

A ₁ , A ₂ .. A _k .. A _{k + 1} , A _K

signal outputs

c ₁ , c ₂ , c ₃ ..c _m ..c _M

parameter

D ₁ , D ₂ .. D _n , D _{n + 1} , D _N

signal outputs

E ₁

entrance

E ₂

output

E ₃

entrance

G ₁ , G ₂

threshold

I _load

load current

I ₂ , I ₁ , I ₀

Load current value

M

measured variable

Out

output

Out _old / out _new

old / new output signal

S _i , S _{i + 1}

control signal

S ₁ , S ₂ ..S _{i + 1} , .S _I

Control signal types

t

Time

t ₁ , t ₂

time

.DELTA.U

correction variable

U _B

supply voltage

AROUND)

internal voltage signal

V

supply line

Claims (9)

1. Method of changing a signal processing in a sensor system, comprising the following features:

   a) a measurement variable (M) is detected, and a sensor signal (U(M)) representing the measurement variable (M) is generated, in a sensor element (12) which is a component of a sensor unit (10),

   b) the sensor signal (U(M)) is processed in a sensor signal processing unit (25), which is similarly a component of the sensor unit (10), according to predetermined parameters (C₁, C₂, C₃, ..., C_m, ... C_M), wherein the parameters (C₁, C₂, C₃, ..., C_m,.... C_M) are set externally,

   c) at least one signal (Out) processed in the sensor signal processing unit (25) is transmitted to an evaluating unit (40) and evaluated therein,

   d) the evaluating unit (40) newly determines on the basils of the transmitted signal at least one of the parameters for signal processing,

   e) the evaluating unit (40) checks the validity of the at least one parameter and determines whether a change of the at least one parameter is required,

   f) the evaluating unit (40) transmits in the case of a required change this at least one parameter (C₁, C₂, C₃, ..., C_m, ... C_M) via a connecting line (A) present between the sensor unit (10) and the evaluating unit (40),

   g) the sensor signal processing unit (25) sets this at least one transmitted parameter (C₁, C₂, C₃, .... C_m, ... C_M) and

   h) in the case of a required change of the at least one parameter (C₁, C₂, C₃,... C_m, .... C_M) this is transmitted in ongoing operation to the sensor signal processing unit (10, 25) only if the transmission of signals (Out) from the sensor signal processing unit (25) is not disrupted by that, so that a constant updating of the parameter set in the sensor signal processing unit is ensured and the sensor system can operate in continuous operation.
2. Method according to claim 1, characterised in that at least the newly determined parameter (C₁, C₂, C₃, ..., C_m, ... C_M) is transmitted by way of a common energy supply line (V) of the sensor system (10) and the evaluating unit (40).
3. Method according to claim 1, characterised in that at least the newly determined parameter (C₁, C₂, C₃, ..., C_m, ... C_M) is transmitted by way of the connecting line (A), by way of which the signal (Out) processed in the sensor signal processing unit (25) is transmitted to the evaluating unit (40).
4. Method according to one of claims 1 and 2, characterised in that at least one parameter (C₁, C₂. C₃, ..., C_m, ... C_M) is transmitted by charge of an output load (I_Last) between the signal processing unit (10, 25) and the evaluating unit (40).
5. Method according to claim 4, characterised in that the output load (I_Last) is changed continuously.
6. Method according to claim 4 or 5, characterised in that the output load (I_Last) is changed in steps.
7. Method according to any one of claims 1 to 6, characterised in that at least one parameter (C₁, C₂, C₃, ..., C_m, ... C_M) is transmitted by a change in the supply voltage (U_B) of the sensor unit (10).
8. Use of the method according to any one of claims 1 to 7 in generally programmable systems.
9. Use of the method according to any one of claims 1 to 8 in measured value detection of magnetic field sensors.

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